Method of moulding metal cylinders



Sept. 22, 1959 c. sci-1WD METHOD OF MOULDING METAL CYLINDERS Filed June19. 1956 lNVENTOR WW ATTORNEYS United States Patent 2,904,863 .1 METHODOF MOULDING METAL CYLINDERS Christoph Schmid, Wietze, Kreis Celle,Germany, assignor to Deutsche Erdiil-Aktiengesellschaft, Hamburg,Germany Application June 19, 1956, Serial No. 592,379

Claims priority, application Germany June 25, 1955 1 Claim. (Cl. 22-202)It is occasionally necessary in industry to have cylinders made of lowmelting metals or alloys, and such cylinders cannot be madesatisfactorily by the customary methods.

Such cylinders are useful, for example, in the mineral oil industry forliquid-tight casings to enclose sample cores which are to be subjectedto flooding tests under the conditions existing in rock strata fromwhich the sample cores have been obtained. These flooding tests arecarried out at high pressures, which may be up to several hundredatmospheres, and at high temperatures of 100 C. or higher, and there areused for making the casings low melting metals or alloys, because thesematerials are capable of expanding in accordance with the changes inshape that the sample cores undergo when subjected to the aforesaidconditions. During the flooding the pressure acting on the exterior ofthe casing is kept a few atmospheres higher than the flooding pressurein the interior of the casing. In this manner bursting of the casingoutwardly from the interior is prevented, and throughout the test thecasing is kept in close contact with the sample core.

Cylinders of easily fusible metals or alloys are usually made by castingthe molten metal into a suitably prepared mould and then bringing aboutsolidification, if desired, by means of suitable cooling devices. Thesample core itself is used as the core of the mould, in order to producea casing that very closely fits the external surface of the sample core.In this manner there is obtained a cylinder having a porous and bubblystructure which cannot withstand the conditions of pressure andtemperature used when the flooding tests are carried out under theconditions existing in the rock strata. Furthermore, the liquid metalpenetrates into the porous rock of the sample core.

In order to produce a pore-free finely crystalline metal casing, and toensure that the metal does not penetrate into the core during casting,it has been recognised that immediate solidification of the molten metalat the external surface of the rock sample is essential, but that, toensure pore-free solidification of the metal casing, the externalsurface of the rock sample must itself be preheated to a temperatureabove ordinary temperature but below the melting point of the metal. Theterm metal is used in the appended claim to include a metal alloy.

In the method of the present invention the casting mould with the rocksample forming the core of the mold is placed in a temperaturecontrolling device and preheated to a temperature above ordinarytemperature ice and below the'melting-point'of the-metal or-alloy. Intothemould,-'-of which the temperature has thus been adjusted, the metalor alloy is introduced at atempera'ture somewhat above, for example,about 15 C. above, its melting point. The difference in temperaturebetween the mould and the melt is sufficient to cause immediatesolidification of the melt at the outer surface of the core without theformation of pores. The molten metal or alloy is introduced into themould by means of a preheated funnel. The temperatures at which themould with its core and the moulten metal or alloy should be maintaineddepend on the melting point of the metal or alloy and on the size andpetrographic properties of the rock sample to be enclosed in the casing.These temperatures are so chosen that, after the molten metal or alloyhas been introduced, it solidifies immediately at the surface of therock core so that it cannot penetrate into the porous rock core. Therapid solidification of the metal or alloy also prevents the penetrationof bubbles of air or gas from the rock core into the metal or alloy, anda finely crystalline metal structure is obtained. Since the metalsolidifies very rapidly when the correct temperatures for carrying outthis invention are used, the pouring funnel must be withdrawn during thecasting operation at a rate corresponding with the rate at which themolten metal or alloy is introduced, but care must be taken that theoutlet end of the tube of the funnel remains continuously below thelevel of the melt.

The method of the invention is described by way of example withreference to the accompanying drawing. In this example, an alloy havinga melting point of 135 C. is used for casting a casing round a rock coreof 55 millimetres diameter having a permeability of about 350 millidarcyand a porosity of about 23 percent. The rock core 1 is held in positionin the centre of a casting mould 2 by means of a clamping screw 6mounted in a bracket 7 fixed to the mould. The mould and core are thenplaced vertically, for example, in a tubular electric oven 3 of suitabledimensions and heated to a temperature C. below the melting point of thealloy. A funnel 5 having a long outlet tube 4 is heated to a temperatureabout 50 C. above the melting point of the alloy, and is insertedimmediately before the casting operation into the space between the rockcore and mould until the lower end of the tube 4 is almost on the bottomof the mould. The alloy is melted and heated to a temperature 15 C.above its melting point. The molten alloy is poured into the funnel, andcare is taken that the latter is always partially filled with alloy.During the casting operation the funnel is withdrawn progressively fromthe space between the core and the mould, while taking care that theoutlet end of the tube 4 remains continuously immersed in the melt. Bythis procedure the escape of easily volatile substances from the coreand through the molten metal, and the consequent formation of pores andbubbles in the cast cylinder, are avoided.

I claim:

A method of moulding a pore-free cylindrical casing of low meltingmetalabout a sample core of a rock stratum to be subjected to a floodingtest, which method comprises preheating a mould and sample core of rock,which forms the core of the mould, in a temperature controlling deviceto a temperature above ordinary temperature and below the melting pointof the metal, heating the metal to a temperature above its meltingpoint, slowly introducing the molten metal into the mould by means of afunnel heated above the said melting point and with its tube extendingsubstantially to the bottom of the mould, and during the castingoperation gradually withdrawing the funnel from the mould at a ratecorresponding to that at which the molten metal is introduced and Whilemaintaining the end of the tube of the funnel continuously immersed inthe rising melt, the difference in temperature between the preheatedcore and the molten metal during the casting operation being *about 90C. and-such as to cause immediate solidification of the melt at theouter surface of the core.

References Cited in the file of this patent UNITED STATES PATENTSWheeler Apr. 26, 1887 Peck Apr. 30, 1889 Ensslen Apr. 30, 1912 DonaldsonFeb. 26, 1929 Townhill Sept. 3, 1957 OTHER REFERENCES

